The present invention relates to a light emitting apparatus having a plurality of light emitting points capable of generating light beams, respectively and, more particularly, to an improvement of a light emitting apparatus for generating a retrieving or recording light beam or an erasing light beam, which is incorporated in an information recording, retrieving, and erasing system for optically recording information, and retrieving and erasing the recorded information.
In an information recording, retrieving, and erasing system for optically recording information, and retrieving and erasing the recorded information, in a recording mode, a recording beam which is intensity modulated in accordance with information to be recorded is focused on an information recording medium, and a recording film of the information recording medium causes a change in phase from a crystal state to a noncrystal state or the crystal structure of the recording film of the information recording medium is changed, thus recording the information. In a retrieving mode, a retrieving beam having a predetermined intensity lower than that of the recording beam is focused on the recording film of the information recording medium, whose phase is changed, or the recording film of the information recording medium, whose crystal structure is changed, thus retrieving the information. In an erasing mode, an erasing beam having a predetermined intensity higher than that of the retrieving beam is focused on the the recording film of the information recording medium, whose phase is changed, or the recording film of the information recording medium, whose crystal structure is changed, thus erasing the information. In general, according to recording and erasing processes on the information recording medium, a circular beam spot is formed on the information recording medium by the recording or retrieving beam, and an elliptic beam spot is formed on the recording medium by the erasing beam. Such a system is disclosed in, e.g., U.S. patent application Ser. Nos. 673764 (now abandoned), 705305 (now U.S. Pat. No. 4,689,781), 713598 (now U.S. Pat. No. 4,694,443), 93644 (now U.S. Pat. No. 4,804,835), 018489 (now abandoned), and 018493 (now U.S. Pat. No. 4,825,064), filed on Nov. 21, 1984; Feb. 25, 1985; Mar. 19, 1985; Dec. 1, 1986; Feb. 25, 1987; and Feb. 25, 1987.
Conventionally, the following two systems are known. One system employs an optical system wherein two light sources, e.g., semiconductor lasers are arranged at different positions to be separated from each other, and laser beams from the two light sources propagate toward an information recording medium along a identical optical path. The other system employs a single light source having light emitting points for emitting light beams, e.g., a semiconductor laser array. In the former system, the optical system is complicated, and becomes bulky. As a result, the weight of an optical head is increased to prolong an access time. In the latter system, one of the two light emitting points of the semiconductor laser array must emit a circular laser beam to form a substantially circular beam spot on the information recording medium, and the remaining light emitting point must emit an elliptic laser beam to form a substantially elliptic beam spot on the information recording medium. However, it is difficult to design the semiconductor laser array so that a substantially elliptic beam spot having a sufficiently large elliptic ratio and a predetermined size is formed on the information recording medium. Even if such a semiconductor laser array can be designed, it is difficult to stably emit both the laser beams.